4. Conclusion
Analysis of iodine by spectrophotometric methods (Sandell and
Kolthoff reaction) in foods with low iodine levels (less than
25 lg/100 g) showed iodine values comparable with those determined
with the standard ICP-MS method. For foods containing
higher iodine contents, especially those containing high sodium
and iron concentrations, spectrophotometric methods showed
much higher values for iodine content than those determined by
ICP-MS (with relative positive bias of 25–122%). A study of the catalytic
effects of sodium and/or iron on the determination of iodine
by Sandell and Kolthoff reaction demonstrated a false positive
effect. Therefore, to achieve reliable and accurate results, ICP-MS
is recommended for iodine analysis in foods, especially for foods
containing high sodium and/or iron concentrations. Users of spectrophotometric
methods based on the Sandell and Kolthoff reaction
for iodine determination in foods need to be aware of the
possible false positive results due to high concentrations of sodium
and/or iron. Additional steps to remove the accelerating minerals
should be included in the analytical process before measurement
of the iodine content